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comparison bn_mp_reduce_is_2k.c @ 1:22d5cf7d4b1a libtommath

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Renaming branch
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:23:46 +0000
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-1:000000000000 1:22d5cf7d4b1a
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis
2 *
3 * LibTomMath is a library that provides multiple-precision
4 * integer arithmetic as well as number theoretic functionality.
5 *
6 * The library was designed directly after the MPI library by
7 * Michael Fromberger but has been written from scratch with
8 * additional optimizations in place.
9 *
10 * The library is free for all purposes without any express
11 * guarantee it works.
12 *
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org
14 */
15 #include <tommath.h>
16
17 /* determines if mp_reduce_2k can be used */
18 int mp_reduce_is_2k(mp_int *a)
19 {
20 int ix, iy, iz, iw;
21
22 if (a->used == 0) {
23 return 0;
24 } else if (a->used == 1) {
25 return 1;
26 } else if (a->used > 1) {
27 iy = mp_count_bits(a);
28 iz = 1;
29 iw = 1;
30
31 /* Test every bit from the second digit up, must be 1 */
32 for (ix = DIGIT_BIT; ix < iy; ix++) {
33 if ((a->dp[iw] & iz) == 0) {
34 return 0;
35 }
36 iz <<= 1;
37 if (iz > (int)MP_MASK) {
38 ++iw;
39 iz = 1;
40 }
41 }
42 }
43 return 1;
44 }
45